1. Field of the Invention
The present invention relates to a process for producing a color liquid crystal display device, and particularly to a process for producing a color liquid crystal display device having a color filter and a black matrix.
2. Related Background Art
As an example of the conventional color liquid crystal display devices having a color filter, may be mentioned a device disclosed in Japanese Patent Application Laid-Open No. 5-257137. This device includes a first glass substrate, a second glass substrate and a liquid crystal charged into a space between both glass substrates. A plurality of switching elements and transparent pixel electrodes electrically connected to the respective switching elements are formed on the first glass substrate, and a color filter is provided on each of the transparent pixel electrodes. Besides, a transparent common electrode is provided on the second glass substrate.
FIG. 18 is a cross-sectional view illustrating the construction on the side of the first glass substrate. As illustrated in this drawing, a thin film transistor (hereinafter referred to as "TFT") 109 composed of a gate electrode 102, a gate insulating film 103, an amorphous silicon film 104, a source electrode 107 and a drain electrode 108 are formed on the glass substrate 101. A transparent pixel electrode 114 is connected to the drain electrode 108. All the elements other than the transparent pixel electrodes 114 are covered with a passivation film 110 composed of a plasma nitride film. Further, a color filter 113 is formed on the transparent pixel electrode 114.
In this construction, gate voltage applied to the gate electrode 102 is changed over high or low upon the operation of image display to turn the TFT 109 On or Off, whereby a display data signal applied to the source electrode 107 is written in the transparent pixel electrode 114. The alignment of liquid crystal molecules is controlled by the action of this writing voltage and voltage applied to the common electrode formed on the second glass substrate (not illustrated) to make display.
In the case of the color liquid crystal display device disclosed in the prior art document, the display data signal is applied to the liquid crystal through the color filter on the pixel electrode, so that the writing voltage undergoes voltage drop due to the interposition of the color filter. Therefore, sufficient voltage is not applied to the liquid crystal, so that contrast characteristics are lowered. In order to ensure satisfactory contrast characteristics, it is necessary to increase the writing voltage. The necessity has invited increase in costs attending upon increase in consumption of electric power and formation of peripheral driving circuits resistant to high voltage.
In the prior art document, the color filter is formed by an electrodeposition process. In the electrodeposition process, the same process must be conducted 3 times in order to form colored layers of R (red), G (green) and B (blue), so that the number of processes increases, which involves disadvantages from the viewpoints of cost and yield.
Japanese Patent Application Laid-Open No. 8-36173 discloses a process for the production of a liquid crystal display device including the steps of providing a color-receiving base layer on a TFT array substrate, subjecting the base layer to patterning of ink receptivity and applying coloring materials for a color filter to the thus-treated layer using an ink-jet apparatus to form a color filter.
However, this process involves disadvantages from the viewpoints of cost and yield because it includes the complicated process of providing the color-receiving base layer and subjecting the base layer to patterning.